1. Field of the Invention
The present invention relates to an apparatus and a method for removing harmonic components. More particularly, the present invention relates to a Harmonic Rejection Mixer (HRM) for removing harmonic components using a plurality of Local Oscillation (LO) frequencies and an operating method thereof.
2. Description of the Related Art
Generally, a mixer is a circuit for performing a function of multiplying two input signals, and is used for down-converting a high frequency Radio Frequency (RF) signal to an Intermediate Frequency (IF) or baseband signal. Also, the mixer is used for up-converting an IF or baseband signal to an RF signal.
FIGS. 1A-1B are views illustrating an output signal of a mixer according to the conventional art.
FIG. 1A illustrates an output signal of a general mixer, and FIG. 1B illustrates an output signal of an HRM.
Generally, a mixer uses a Local Oscillation (LO) signal in order to up-convert or down-convert an input signal. The LO signal may include a harmonic component in a frequency which is an odd number-multiple of a basic frequency. Accordingly, an output signal generated by the mixer includes a harmonic component by a frequency which is an odd number-multiple (3LO, 5LO, 7LO) of a basic frequency of an LO signal.
In case of using an HRM to prevent a harmonic component from occurring, a third order harmonic component and a fifth order harmonic component may be removed as illustrated in FIG. 1B. For example, the HRM may remove a harmonic component by combining output signals generated using LO signals having the same frequency but having different phases of 0 degree, 45 degree, and 90 degree at respective mixers. At this point, the HRM may minimize a noise by a harmonic component by setting a gain of a mixer that uses an LO signal of 45 degree to 1.4 multiple of another mixer.
As described above, the HRM can remove a harmonic component by combining output signals of mixers that use different phases. That is, mixers included in the HRM are connected in a mutual supplementary manner to generate one output. Accordingly, in the case where one of mixers included in the HRM is turned off for power control, a phase and a weight should be set again using the rest of the mixers.